In the related art, a selective catalytic reduction (SCR) system that reduces NOx into nitrogen and water using ammonia is known as one of many systems that purify exhaust gas from vehicles.
In addition, zeolite is known as a material that adsorbs ammonia in the selective catalytic reduction system.
PTL 1 discloses a honeycomb structure including a honeycomb unit that contains zeolite, an inorganic fiber and/or whisker, and an inorganic binder.
Meanwhile, SAPO-34 is known as zeolite having excellent NOx purification performance.